James mckechnie



' J. McKECHNlE. TWO-STROKE INTERNAL COMBUSTION ENGINE,

APPLICATION FILED MAY 1, I918- Patented 001. 14,1919.

Inventor.

UNITED STATES PATENT OFFICE.

JAMES MOKECHNIE, 0F BAR-ROW-IN-FURNESS, ENG-LAND, ASSIGNOR T0 VIGKERS LIMITED, OF WESTMINSTER, ENGLAND.

Specification of Letters Patent.

Patented Oct. 14, 1919.

Application filed May 1, 1918. Serial No. 231,843.

T 0 all whom it may concern:

Be it known that I, JAMES MCKEGHNIE, a subject of the King of Great Britain, residing at Naval Construction Works, Barrowin-Furness, in the county of Lancaster, England, have invented certain new and useful Improvements in or Relating to Two-Stroke Intcrnal-Combustion Engines, of which the following is a specification.

This invention relates to two-stroke internal combustion engines, and has for its chief object to reduce the loss of scavenging air and thus to increase the efficiency of the engine. In engines of this kind, whether of the single or opposed piston type, in which the exhaust escapes through ports covered and uncovered by the piston, a considerable loss of scavenging air takes place through the open ports and the amount of air left in the cylinder for compression is measured from the cut-off or closing of the exhaust ports by the piston on the compression stroke. To obtain increased compression and resulting increase of power in the engine the pressure of the scavenging air has been raised, but this involves'the use of additional power for driving the pump and still leaves the efficiency of the engine low.

According to this invention, I provide, as close to each cylinder as is practicable, an exhaust controlling valve so actuated as to give full exhaust opening but closing to check or throttle the escaping gases before the closing of the exhaust ports by the piston. Any suitable construction of valve may be employed, but a convenient arrangement comprises a disk valve rotating about a diametrical axis at the same speed as the crankshaft and adjusted to give the full opening and the required throttling action at the proper points of the piston stroke. Means, such as eccentric or elliptical gearing, may be employed to give the best timing for the free exhaust and throttling operations where constant speed of rotation of the valve is undesirable.

In order that the said invention may be clearly understood and readily carried into effect, I will describe the same more fully with reference to the accompanying drawings, in which Figure 1 is an elevation of an engine showing the position of the exhaust controlling valve and a convenient method of driving it.

Figs. 2 and 3 illustrate a form of rotating disk valve which may be employed.

Fig. 4 shows a modified form of rotating forming a valve casin is fitted and. the

valve shown in the ollowing figures is placed in the said casing or exhaust pipe. The spindle d of the valve, which is assumed to be of rotating type, is provided with the bevel wheel d with which engages the bevel wheel 0 on the shaft E, the other end of which is driven through bevel gearing. f

from the crank shaft F of the engine. This gearing gives a constant speed rotation to the throttling valve but eccentric or elliptical gearing may be substituted for the simple bevel gearing shown in order to give'the best timing for the throttling operation of the valve.

Referring to the valve shown in Figs. 2

and 3 the exhaust passage 0 passing through the valve casing or exhaust pipe C is provided with the rotating disk valve D mounted centrally upon the spindle d, which may be driven as shown in Fig. 1. The disk valve when in the position shown, in which it extends laterally across the passage 0, does not quite close the passage and allows the exhaust gases to pass through the narrow annular channel surrounding the disk, this restricted passage giving a pronounced choking action to the gases so that the rcssure in the cylinder A at the end of ex aust is substantially above atmospheric pressure. The timing of the valve D is arranged so that the valve approaches the maximum.

throttling position some time before the engine piston closes the exhaust ports and the throttling takes place during the entry of the scavenging air. The complete closing of the exhaust by the engine piston occurs approximately at the position of maximum throttling by the valve D.

For reversing purposes the gearing driving the valve D need not be altered unless it is desired to develop full power on re-.

verse, in which case spiral gearing could be fitted on the shaft E or the valve spindle d to allow of an altera ion relatively to the crank shaft of the engine, Thus when the crank shaft is on the dead center with fully open exhaust ports the valve may be advanced to the position indicated by the line m for the forward driving of the engine and the valve may be brought by the spiral gearto the position 3/ when the engine is re gases ed across tli is the lent,

T w v 1 w an snown in z i r is of cylindric throu h end, -re par r e --ontraoted end 01' the p: isage ssitg over the opening of the eas prolong the period of matznnnn the exhaust pipe C is formed with a cylindrical portion corresponding to the valve, which however leaves a small annular clearance so that when the valve is not across the passage 0 the gases can still escape, though at a greatly reduced rate. This valve is rotated as in the case of the disk valve already described.

lln the modification shown in Fig. 7 an ordinary mushroom valve D is employed. under the control of the cam E, which is so formed as to open the valve D fully during the earlier stages of the exhaust and to allow it almost to close during the final stages, under the action of the spring 0, to provide for the desired throttling effect without actually cutting off the exhaust until the exhaust port is closed by the engine piston.

In Fig. 8 an automatic valve D is shown consisting of a flap hinged at 03* and extending across the passage 0, the valve being normally held in the position shown in full lines by means of the spring 03 acting through the arm (Z on the valve spindle. In the closed position the valve does not completely obstruct the passage 0 but allows a restricted channel through which the exhaust gases during the final stage of the ex haust are allowed to flow, but during the early stage, when the exhaust pressure is considerable, the valve D is moved back against the force of the spring into a fully open position such as is shown in dotted lines, closing automatically as the pressure of the exhaust gases falls. The throttling action can be adjusted to any required extent by varying the strength of the spring (5 so that the valve may be set to give the best throttling effect as found by experiment A valve arrangement in accordance with this invention allows of reduction both in quantity and pressure of the scavenging air while providing for suilicient compression and the efficiency of the engine is correly increased by the power saved in ior of the scavenging pump.

cla n and desire to secure by Lettent of the United States is a two-stroke internal crim'lbustion on o iston, a cylinder provided with a ort controlled by the piston and an exhaust control ng valve adapted to be so me full exhaust opening and small clearance when closed losing before the closing of the by the piston it provides a 4 channel for the v which d as they escape jut of the exhaust port by tne pix in a two-stroke internal con'ibustion ena piston, a cylinder provided with an cxlniust port controlled by the on, an ex liaust channel, and a rotatable exhaust controlling valve in the said channel adapted to open the exhaust channel during the earlier stages of the exhaust but provided with a small clearance when closed so as only partially to close the said channel during the later stages of the exhaust, to throttle the gases before the exhaust is completely cut oil by the engine piston.

3. in a two-stroke internal combustion engine, a piston, a cylinder provided with an exhaust port controlled by the piston, an exhaust channel, a rotatable exhaust controlling valve in the said channel having a small clearance when in closed position and means for rotating the said valve so as to close it before the exhaust port is closed by the piston.

4. In a two-stroke internal combustion engine, a piston, a cylinder provided with an exhaust port controlled by the piston, an exhaust channel, a rotatable disk valve in the said channel between which and the valve a restricted passage is left when the valve is transversely across the channel, and means for rotating the said disk valve. 

